1. Field of the Invention
This invention is directed to a method for treating obstructive sleep apnea. More particularly, this invention is directed to a combination treatment for obstructive sleep apnea. Further, this invention is directed toward a combination treatment for obstructive sleep apnea to improve patient compliance with a positive airway pressure treatment.
2. Description of the Prior Art
A. Obstructive Sleep Apnea
Obstructive sleep apnea (OSA) and other sleep disordered breathing conditions have received increased scientific and academic attention. Sleep apnea is characterized by excessive periods of cessation of breathing during sleep. In addition to the inconvenience of daytime sleepiness, obstructive sleep apnea can be associated with significant health consequences including adverse cardiac effects.
OSA patients are generally characterized by degree severity according to a score referred to as an apnea-hypopnea index (AHI) which is a measure of the patient's number of apnea-hypopnea events per hour of sleep. For example, an AHI of 30 represents, on average, 30 such events per hour. While there is no fixed agreement on characterization of the disease severity levels, an AHI less than 10 is generally considered normal. An AHI of 10 to 30 is generally considered mild to moderate. A higher AHI is generally considered severe. Severe OSA patients may experience excessive daytime sleepiness, elevated blood pressure and reduced saturated oxygen levels in the blood.
A patient's AHI is measured during a sleep study in which a sleeping patient's apnea-hypopnea events, saturated oxygen levels and other factors are recorded. Sleep studies (polysomnographies) are performed in a sleep lab where a patient spends the night in the lab with sleep parameters monitored and recorded. Sleep studies may also be performed at home. An example of such is described in U.S. Pat. No. 6,216,702 issued Apr. 17, 2001 (assigned to Camtech AS, Norway).
B. Positive Airway Pressure Treatment
A common treatment for obstructive sleep apnea is positive airway pressure (PAP) treatment. In a PAP treatment, air is delivered under pressure to an OSA patient's airway during sleep. The pressurized airflow maintains patency of the patient's airway preventing airway collapse otherwise associated with OSA. Examples of PAP machinery are shown in U.S. Pat. No. 6,752,151 (assigned to Respironics, Inc., Murrysville, Pa.); U.S. Pat. No. 6,516,802 (assigned to Mallinckrodt, Inc., St. Louis, Mo.) and U.S. Pat. No. 6,763,629 jointly assigned to New York University, New York, N.Y. and Puritan-Bennett Corp., Pleasanton, Calif.).
A PAP treatment may take any one of a number of different forms. Most commonly, the PAP is a continuous positive airway pressure treatment (CPAP) (sometimes referred to as fixed continuous airway pressure). In this treatment, the patient wears a mask covering the nose and mouth. Air is supplied under constant pressure to the mask.
The necessary pressure of the airflow for an effective PAP treatment varies from patient to patient. The setting of the pressure (referred to as “titration”) is normally set during a sleep study to find the appropriate pressure for the particular patient to maintain patency.
When used in accordance with a physician's instructions, CPAP can be a very effective treatment for obstructive sleep apnea. However, patient compliance with a CPAP treatment can very low. In addition to not using a CPAP machine on certain nights, the patient may not use the machine for the whole night.
Low CPAP compliance can be attributed to many factors. The mask can be uncomfortable, the noise of the pressurization machine associated with the mask can be disruptive to sleep and the pressurization itself can result in unpleasant side effects such as nasal or throat dryness. Further, bed partner intolerance poses a problem for compliance with a CPAP therapy. A bed partner may complain about the noise of the CPAP machine. Placing a CPAP machine further from the bedside may reduce this disturbance. However, this results in a longer tubing and increased pressure drop in the CPAP machine which can reduce the effectiveness of the CPAP machine.
C. Non-PAP Treatments for OSA
i. Appliances and Invasive Surgery
Historically, other treatments for OSA include oral appliances and surgery. Surgical treatments include uvulopalatopharyngoplasty (UPPP) in which the trailing edge of the patient's soft palate is trimmed (e.g., by about 1 cm). These procedures have varying success rates.
Oral appliances also require patient compliance. In at least one study of a removable appliance, the appliance was found to be less effective than CPAP (especially in severe OSA patients) even though it was not as bothersome to patients. Clark, et al., “A Crossover Study Comparing the Efficacy of Continuous Positive Airway Pressure with Anterior Mandibular Positioning Devices on Patients with Obstructive Sleep Apnea”, Chest, 109 (6) pp. 1477-83 (June 1996).
Historical surgical options such as UPPP are invasive and painful. Further, if not successful, a UPPP may compromise a patient's ability to benefit from a CPAP treatment. Mortimore, et al., “Uvulopalatopharyngoplasty May Compromise Nasal CPAP Therapy In Sleep Apnea Syndrome”, Amer. Journal of Respiratory and Critical Care Medicine, 154 (6 Pt 1) pp. 1759-62 (December 1996). In Mortimore et al., patients with a prior UPPP could tolerate only a much lower CPAP pressure than non-UPPP patients. However, Seemann et al., “Combination Surgical and Mechanical Therapy for Refractory Cases of Obstructive Sleep Apnea”, Journal of Otolaryngology, Vol. 31, No. 2, pp. 85-88 (2002), report an average decrease of 4.8 cm H2O CPAP titration pressure after laser-assisted uvulopalatoplasty (LAUP) (one of the five reported patients experienced a CPAP pressure decrease of 11 cm H2O). A LAUP procedure is less aggressive than a UPPP and scars the exterior surface of the mucosa. This scarring can stiffen the palate but is painful.
ii. Less Invasive Surgery (RF Ablation and Palatal Implants)
Recently, less invasive surgical treatments have been suggested for treatment of obstructive sleep apnea. For example, in Blumen, et al., “Radiofrequency Ablation for the Treatment of Mild to Moderate Obstructive Sleep Apnea”, Laryngoscope, pp. 2086-2092 (2002), the authors suggest using radio-frequency ablation of the soft palate as an effective treatment for obstructive sleep apnea patients. The radio-frequency ablation of the soft palate is described in U.S. Pat. No. 5,456,662 issued Oct. 10, 1995 (describing radiofrequency ablation of the soft palate to treat snoring).
The United States Food and Drug Administration (FDA) has issued 510(k) clearance No. K040417 for the treatment of mild to moderate obstructive sleep apnea to Restore Medical Inc., St. Paul, Minn., USA (assignee of the present application) for the use of its Pillar® palatal implant treatment. The Pillar® implant is an implant placed in the soft palate to stiffen the soft palate through fibrotic response of palatal tissue to the implant material. The Pillar® implant is described in assignee's related U.S. Pat. No. 6,513,530 issued Feb. 4, 2003.
The efficacy of the Pillar® implant in the treatment of obstructive sleep apnea is reported in a poster entitled “Efficacy of the Pillar® Palatal Implant System: First Results in OSA Patients” by Hein, et al., and presented at the Annual Meeting of the American Academy of Otolaryngologist in New York, N.Y., USA (September 2004). For patients with mild to moderate OSA (i.e., patients having an AHI of 10 to 30 episodes per hour), the Hein, et al., poster reports a mean decrease in AHI of 53.4% as well as a reduction in daytime sleepiness and snoring intensity for those patients reporting an AHI decrease. Of 16 treated patients, 13 experienced an AHI decrease.
A palatal implant such as the Pillar® implant for treating obstructive sleep apnea has many advantages over PAP treatment. A Pillar® implant is placed in the soft palate in a single procedure (commonly three implants are placed in the soft palate during one office visit to an otolarnygologist). After a short recovery period (usually a matter of a few days in which the patient is treated only with a mild pain reliever such as aspirin or the like), the patient has no lasting discomfort from the implant or its placement procedure and no further therapy is needed. This has clear advantages over a CPAP procedure in which the patient must, every night, wear the CPAP device and comply with the CPAP therapy.
iii. Severe OSA Patients and Modifications to PAP to Improve Compliance
Not withstanding its significant advantages, a palatal implant for the treatment of obstructive sleep apnea may not be suitable for all OSA patients. Currently, the Pillar® procedure is only cleared for market release by the FDA for patients who suffer from mild to moderate obstructive sleep apnea.
For patients with severe OSA, CPAP remains the preferred treatment. Unfortunately, CPAP suffers from low patient compliance.
Also, for many OSA patients, the CPAP must be set at a high operating pressure in order to be effective. According to some investigators, the high operating pressure increases a likelihood of low compliance. For patients who cannot tolerate CPAP, historical invasive surgeries remain a painful option. Souter, et al., “Upper Airway Surgery Benefits Patients with Obstructive Sleep Apnoea Who Cannot Tolerate Nasal Continuous Positive Airway Pressure”, Journal of Laryngology and Otology, 118 (4), pp. 270-4 (April 2004).
Advances have been made in PAP treatments. These include delivery of the pressured air nasally (nCPAP) or through an oral appliance in efforts to increase comfort and compliance. Nasal CPAP still suffers from low compliance. Berthon-Jones, et al., “Nasal Continuous Positive Airway Pressure Treatment: Current Realities and Future”, Sleep, 19 (9 Suppl) S131-5 (November 1996) report nCPAP as an effective treatment but with a patient dropout rate of 30% and a usage of less than 5 hours per night.
One paper reports on efforts to improve compliance with nCPAP by setting the treatment pressure at an initial low pressure (3 cm H20) and ramping the pressure up over 45 minutes to permit the patient to fall asleep before the higher and more uncomfortable prescribed pressure is administered. However, that paper reports a severely limited effective therapy. Pressman, et al., “Ramp abuse. A Novel Form of Patient Noncompliance to Administration of Nasal Continuous Positive Airway Pressure for Treatment of Obstructive Sleep Apnea”, American Journal of Respiratory and Critical Care Medicine, 151 (5) pp. 1632-4 (May 1995). Pressman, et al., report a compliance rate for nCPAP varying between 46% to 89%.
Advances also include auto-titrating positive airway pressure (APAP) machines. Frequently, these advances are costly alternatives to traditional CPAP and have there own clinical issues.
Unlike CPAP machines having a constant pressure setting, the APAP machine may vary the pressure over the night in response to timing or sensed parameters. APAP has been used in nCPAP. See, Berthon-Jones, et al., article, supra, where the auto-titration is believed to reduce the mean delivery pressure thereby reducing side effects and increasing patient compliance.
Some authors claim that auto-titration supports a conclusion that a lower operating pressure leads to improved compliance. Hudgel, et al., “A Long-Term Randomized, Cross-Over Comparison of Auto-Titrating and Standard Nasal Continuous Airway Pressure”, Sleep, 23 (5) pp. 645-8 (August 2000). Hudgel, et al., report APAP had a lower average pressure than CPAP (6.4 v. 10.6 cm H2O) and APAP had a greater average daily machine use (6.0 v. 5.5 hours). See, also, Massie, et al., “Comparison Between Automatic and Fixed Positive Airway Pressure Therapy in the Home”, American Journal of Respiratory and Critical Care Medicine, 167 (1) pp. 20-3 (January 2003). Massie, et al., suggest patients who require higher fixed CPAP pressures use auto-titrating CPAP more and report greater benefit from this therapy.
Other authors report comparable overall compliance between APAP and CPAP. Hukins, et al., “Comparative Study of Autotitrating and Fixed-Pressure CPAP in the Home: A Randomized, Single-Blind Crossover Trial”, Sleep, 27 (8) pp. 1512-7 (December 2004). Hukins, et al., report higher compliance with APAP for those patients who reported side effects. Also, the authors reported APAP had lower pressures resulting in lower pressure leaks and fewer reported side effects.
To date, comparative studies of APAP and CPAP have not been conclusive. For example, one study claims APAP is not associated with fewer side effects, better compliance or better satisfaction. Hussain, et al., “A Randomized Trial of Auto-Titrating CPAP and Fixed CPAP in the Treatment of Obstructive Sleep Apnea-Hypopnea”, Respiratory Medicine, 98 (4) pp. 330-3 (April 2004). Differences may be due to different APAP technologies used in different studies. Berry, et al., “The Use of Auto-Titrating Continuous Positive Airway Pressure for Treatment of Adult Obstructive Sleep Apnea”, Sleep, 25 (2) pp. 148-73 (March 2002) (an American Academy of Sleep Medicine review).
Therapeutically effective operating pressures for a PAP vary from patient to patient. As the pressure rises, a patient's ability to tolerate the CPAP treatment is reduced. For example, patients frequently have difficulty tolerating a CPAP titrated above a pressure of about 11 cm H2O. At such pressures, compliance is estimated at about 30%. For low pressures (about 4 cm H2O), compliance is estimated to be much higher (about 90%). At higher pressures (e.g., about 20 cm H2O), compliance rates are estimated to be as low as 10%. It will be appreciated these estimates are aggregates for the patient population. An individual's pressure threshold leading to low compliance will vary from patient to patient. A higher compliance rate at a lower pressure setting is probably due to the reduction of pressure related side effects such as nasal or throat dryness. Also, patients may have difficulty exhaling against a fixed pressure.
It is an object of the present invention to coordinate a tissue stiffening procedure with a positive airway pressure treatment to better treat patients with severe obstructive sleep apnea.